The Hemopump is a catheter-based temporary ventricular assist device consisting of an axial flow pump component at the distal end of the catheter powered by an external motor via a flexible drive cable that runs the length of the catheter. The distal tip of the axial flow pump component is advanced from a femoral artery into the left ventricle (Fig 20-6). When it is in operation, forward blood flow is generated by blood entering the axial flow pump component in the left ventricle and exiting in the aortic arch. Laboratory investigation in a cardiac arrest model has demonstrated sustained mean arterial pressures of approximately 60 mmHg and cardiac output averaging 2.3 L/min.18 The major drawback with the use of this device in the setting of cardiac arrest is that one must be able to insert the catheter from a femoral artery to the left ventricle.
Aortic Catheter Perfusion Techniques
During the past decade, there has been an interest in the use of aortic balloon occlusion catheters to enhance vital organ perfusion during cardiac arrest. The use of standard intraaortic balloon pumping has been shown to increase CPP during closed-chest CPR, but the effect is not dramatic. However, the use of aortic balloon catheters for the infusion of resuscitation solutions during cardiac arrest holds greater promise for improving resuscitation outcome.
Selective aortic arch perfusion (SAAP) as described by Manning et al19 or selective aortic perfusion and oxygenation (SAPO) as described by Paradis et al20 uses a large-lumen balloon occlusion catheter positioned in the descending aortic arch to provide selective perfusion of the heart and brain during cardiac arrest ( Fig 20-7).
The catheter is inserted into a femoral artery (percutaneously or via a cutdown) and blindly advanced into the thoracic aorta. With the balloon inflated and pressure cuffs applied to the upper arms, the coronary and cerebral circulations are relatively isolated for brief perfusion. The resuscitation solution infused consists of an oxygenated blood substitute, such as a perfluorocarbon emulsion or polymerized hemoglobin solution, that might contain various agents to enhance restoration of spontaneous cardiac contraction, maintain neuronal viability, and limit both myocardial and neuronal reperfusion injury. One of the major advantages of SAAP is the ability to administer agents to combat reperfusion injury at the moment of reperfusion or just prior to it. SAAP was designed for use in the prehospital as well as the in-hospital setting. Although laboratory results have been very favorable, the efficacy of this invasive perfusion technique in human cardiac arrest has not been studied.
FIG. 20-7. Selective aortic arch perfusion (SAAP). Positioning of the SAAP balloon occlusion catheter at the end of the descending aortic arch through a femoral artery. Placement of the balloon at this level restricts flow to aortic arch vessels including coronary arteries. (From Manning et al, 19 with permission).
Tang et al have described the use of a balloon occlusion catheter positioned in the ascending aortic arch. 21 Laboratory investigations of this technique have shown marked increases in coronary perfusion with intermittent balloon occlusion. Infusion of fluid via the catheter results in isolated coronary artery perfusion. The technical feasibility of rapidly and reliably positioning the tip of this catheter in the ascending aortic arch may prove to be a significant challenge in the clinical setting.
In 1995, Buckman et al reported the use of a relatively simple device for the rapid initiation of internal cardiac compression through a small thoracic incision. 22 The technique, called minimally invasive direct cardiac massage, uses a rectangular, curved, padded plate connected to a handle to compress the heart through an intercostal incision at the anterolateral left chest at the level of the lower sternum ( Fig 20.-8.). In a swine cardiac arrest model, the device generated CPP and cardiac output similar to that produced by manual open-chest cardiac massage. It has been suggested that a modified device could potentially be inserted via a smaller (2 to 3-cm) intercostal incision.
FIG. 20-8. The heart-contacting baseplate and a portion of the stem of the cardiac compressive device are inserted into the thorax through a small, parasternal incision. The manually-operated handle remains outside the chest. The base plate is positioned directly on the cardiac ventricles, lying within an intact pericardium. Manual depression of the device compresses the heart and produces an artificial systole.
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